repository: Refactor Config

repository/config.go

@@ -0,0 +1,87 @@
+package repository
+
+import (
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"io"
+
+	"github.com/restic/restic/backend"
+	"github.com/restic/restic/chunker"
+	"github.com/restic/restic/debug"
+)
+
+// Config contains the configuration for a repository.
+type Config struct {
+	Version           uint        `json:"version"`
+	ID                string      `json:"id"`
+	ChunkerPolynomial chunker.Pol `json:"chunker_polynomial"`
+}
+
+// repositoryIDSize is the length of the ID chosen at random for a new repository.
+const repositoryIDSize = sha256.Size
+
+// RepoVersion is the version that is written to the config when a repository
+// is newly created with Init().
+const RepoVersion = 1
+
+// JSONUnpackedSaver saves unpacked JSON.
+type JSONUnpackedSaver interface {
+	SaveJSONUnpacked(backend.Type, interface{}) (backend.ID, error)
+}
+
+// JSONUnpackedLoader loads unpacked JSON.
+type JSONUnpackedLoader interface {
+	LoadJSONUnpacked(backend.Type, backend.ID, interface{}) error
+}
+
+// CreateConfig creates a config file with a randomly selected polynomial and
+// ID and saves the config in the repository.
+func CreateConfig(r JSONUnpackedSaver) (Config, error) {
+	var (
+		err error
+		cfg Config
+	)
+
+	cfg.ChunkerPolynomial, err = chunker.RandomPolynomial()
+	if err != nil {
+		return Config{}, err
+	}
+
+	newID := make([]byte, repositoryIDSize)
+	_, err = io.ReadFull(rand.Reader, newID)
+	if err != nil {
+		return Config{}, err
+	}
+
+	cfg.ID = hex.EncodeToString(newID)
+	cfg.Version = RepoVersion
+
+	debug.Log("Repo.CreateConfig", "New config: %#v", cfg)
+
+	_, err = r.SaveJSONUnpacked(backend.Config, cfg)
+	return cfg, err
+}
+
+// LoadConfig returns loads, checks and returns the config for a repository.
+func LoadConfig(r JSONUnpackedLoader) (Config, error) {
+	var (
+		cfg Config
+	)
+
+	err := r.LoadJSONUnpacked(backend.Config, nil, &cfg)
+	if err != nil {
+		return Config{}, err
+	}
+
+	if cfg.Version != RepoVersion {
+		return Config{}, errors.New("unsupported repository version")
+	}
+
+	if !cfg.ChunkerPolynomial.Irreducible() {
+		return Config{}, errors.New("invalid chunker polynomial")
+	}
+
+	return cfg, nil
+}